I’m trying to understand the significance of an error message I get in my 5.1 home theatre sound system when I run the optimizer program using the included microphone.
The program gives a phase error warning for both the rear speakers. I did check all the connections VERY carefully and had not made any mistakes while wiring. So, I tried reversing the polarity on these and rerunning the program, and it now reports all is well.
My system comprises:
Yamaha 5.1 A/V Home Theatre Receiver RX-V385BL
Polk Signature Elite ES10 speakers for front left & right
Sony SSCS8 2-Way 3-Driver Center Channel speaker for front center
Cambridge Audio Minx X-201 Active Subwoofer
Rocketfish Wireless Rear Speaker Kit
Rockville Cube speakers for rear left & right
I suppose it might be that these Rockville Cube speakers are designed with a nonstandard polarity. Or, it might be that the Rocketfish bluetooth gadget (which saves running cables between the front and rear of the room) inverts the polarity. Either would be surprising, but they are certainly possible. I find it significant that BOTH the rear speakers report backwards polarity; having just one of them backwards would strongly suggest a wiring error.
The receiver instructions say that if the program reports a polarity error, and you check all the wiring and can find no problem, then you should leave it as is, and ignore the polarity error. I’ve tried it both ways; right now the wire polarity is reversed in one spot and the program reports all is well. I can imagine rationales for doing either (wires correct and program reports error, or, wires swapped and program reports it is happy). What I’m looking for here is additional insight about how all these things function, to guide my choice. (This insight would be Factual, though if this thread veers into Opinion I don’t necessarily mind.)
Note that the program uses white(ish) noise and frequency sweeps when it runs. One of the several things it does is figure time delay for each speaker to the listener’s position. At a particular frequency, polarity reversal and a different time delay are indistinguishable – but the time delay would have to be different for each frequency, so I can’t imagine the program confuses the two.
Hmm. I can’t say exactly how the phase detection is working, but most likely it is measuring the DB level of the noise and if it drops when certain combinations of speakers are used. If they are out of phase, it will drop.
If you don’t want to rig up a DB meter and test it, your ears can detect the phase interference, at least in a stereo setup. With phase cancellation in music, it will generally sound thinner at certain frequencies. This video has an example of it at 1:55. He’s switching the polarity of the recording in that example, but the effect is similar. At the end of the video, he sweeps a mic back and forth between out of phase speakers, and you get to hear the neato phaser sweep.
It seems unlikely, but maybe the Bluetooth system is introducing enough lag that the phase is that far out. There may be some delay or phase settings in your system that you have not discovered?
Surround systems sometimes have them. There could also be a large amount of reflected waves getting read as out of phase.
That was my guess too… Bluetooth introduces quite a LOT of lag unless every part of the system supports “aptX Low Latency” or similar. IIRC, Rocketfish is Best Buy’s in-house budget brand? I’d be surprised if it does low-latency. But on the other hand, if this is the kit you’re talking about, it doesn’t say it uses Bluetooth at all, just some unknown 2.4 GHz system (which probably works way better than Bluetooth). It does have L/R speaker inputs on the back; might those be reversed?
Or can you try wiring them and seeing if it makes a difference, just for testing?
Oops – I made a mistake in my post, and you have caught it. Yes, Rocketfish is Best Buy’s in house brand. And, as you speculate, what I bought is their rear speaker wireless kit, and it doesn’t say Bluetooth. So, Bluetooth latency does not appear to be an explanation for what I’ve observed. Thank you!
Note that a single value of delay wouldn’t appear to be a phase inversion over a range of frequencies, and by using white(ish) noise and frequency sweeps they are making a range of frequencies available to their analysis program. They could have not bothered measuring them, but this seems unlikely.
As to the inputs on the back (of the sender), they are not reversed. None of my connections were reversed when I checked them and got the error message. I did reverse them for the sake of experiment in exactly one location, the back of the Rocketfish radio receiver, and this did make the error message go away. The puzzle for me is which way of connecting is better.
I’ve also toyed with various ways of testing this. I actually own an oscilloscope, but I actually haven’t thought of a way to completely test this using it. I could test the more limited question of whether the Rocketfish thing reverses the polarity. I could also swap front versus rear speakers, on just one side perhaps, which could test the more limited question of whether the little rear speakers define polarity differently.
All that being said, either of these explanations seem so unlikely – why would a major audio company just swap the labeling on their terminals? What could possibly be a reason? It certainly doesn’t save them any money and I can’t think of an advantage to it!
I dug around some more and it looks like this is a frequent issue with Yamaha’s optimization program (YPAO). Recommended practice is to verify no wiring errors, and then run the optimization and use the result, ignoring the warning.
“Due to variances in speaker construction and room acoustics, it is possible for YPAO to give this warning in error. If the speaker wire is not connected in reverse, the warning can be ignored.”
[usafaq]
“Since this is just a “warning” message and not an “error” message, the test can continue. Many times, due to sound bouncing off items like furniture, walls, etc. the sound that the microphone picks up appears to be out of phase. This should be considered as a normal operation and as long as you have verified the wiring is correct it will be okay.”
[usafaq]
“This message may appear even when everything is connected correctly, depending on the kind of speakers and installation environment. Save the settings and use the system as-is.”
[R-N1000A | Error and warning messages]
My older Sony system gave such an error a few times. But not always. Not a lot of tests to get a good percentage. But my new Sony amp, with all the same speakers and wiring has not. All is hard wired. But room acoustics have changed. Maybe my older system had issues with that. Or the new one just has an improved method.
Bumping this up because I re-found a useful reference for tuning with Yamaha home theatre systems. This contains some useful information about Yamaha’s YPAO (Yamaha Parametric Acoustic Optimizer) present in their home theatre offerings for many years. It includes an article addressing use of wireless speakers.
They are also pushing a digital book for $11 that promises to be the ultimate guide to Yamaha’s system. I have no idea if it is any good, I have never bothered to buy it, but still might. But the articles on the site are worth a read.
(My interest is because I have a now ageing but very good Yamaha receiver I bought from my brother when he upgraded to a full Atmos installation. I got it for pennies on the dollar as they say.)
